Estimate how long it takes to reach a goal weight with a daily calorie deficit, and the date you could get there. The result is a planning estimate. Free, private, and runs entirely in your browser.
Each pound of body weight is treated as about 3,500 kilocalories (7,700 per kilogram). Dividing the energy to lose by your daily deficit gives the number of days, and adding those days to today gives a target date.
Is the 3,500 calorie rule accurate? It is a rough average that works for short periods. Over months your body adapts and burns less, so losses usually slow down.
How fast is safe? Many health agencies suggest about 1 to 2 lb (0.5 to 1 kg) a week for most adults. Faster loss should be supervised.
A person who weighs 180 lb wants to reach 165 lb with a deficit of 500 kcal a day. They need to lose 15 lb × 3,500 = 52,500 kcal, which takes 52,500 ÷ 500 = 105 days, or 15 weeks, at about 1 lb per week.
How do I create a deficit? By eating fewer calories, moving more, or a mix of both. A modest deficit is easier to keep up.
Does it work for gaining weight? Not directly. Use the same idea with a surplus and a goal above your current weight, though this tool expects a loss goal.
The 3,500-calorie-per-pound rule goes back to a 1958 paper by Max Wishnofsky, who estimated the energy content of a pound of body tissue. It remains a handy approximation, but later research showed that bodies adapt to lower intake, so predicted losses over long periods tend to be too high.
Use this calculator to set a realistic timeline and to see how changing the deficit moves your target date. If you have a medical condition, are pregnant, or are under 18, speak with a health professional before changing your intake.
What deficit should I choose? Many people use 250 to 500 kcal a day for a gradual loss. Your own needs depend on your size and activity.
Why did my weight stall? Water balance, a smaller body needing fewer calories, and tracking errors can all slow progress.